The following abbreviations are herewith defined, at least some of which are referred to within the following description.
3GPP Third Generation Partnership Project
ACK Positive-Acknowledgment
BLER Block Error Ratio
BPSK Binary Phase Shift Keying
CAZAC Constant Amplitude Zero Auto Correction
CCA Clear Channel Assessment
CCE Control Channel Element
CP Cyclic Prefix
CQI Channel Quality Information
CSI Channel State Information
CSS Common Search Space
CWS Contention Window Size
DCI Downlink Control Information
DL Downlink
eCCA Enhanced Clear Channel Assessment
eNB Evolved Node B
EPDCCH Enhanced Physical Downlink Control Channel
ETSI European Telecommunications Standards Institute
FBE Frame Based Equipment
FDD Frequency Division Duplex
FDMA Frequency Division Multiple Access
FEC Forward Error Correction
HARQ Hybrid Automatic Repeat Request
LAA Licensed Assisted Access
LBE Load Based Equipment
LBT Listen-Before-Talk
LTE Long Term Evolution
MCL Minimum Coupling Loss
MCS Modulation and Coding Scheme
MU-MIMO Multi-User, Multiple-Input, Multiple-Output
NACK or NAK Negative-Acknowledgment
OFDM Orthogonal Frequency Division Multiplexing
PCell Primary Cell
PBCH Physical Broadcast Channel
PDCCH Physical Downlink Control Channel
PDSCH Physical Downlink Shared Channel
PHICH Physical Hybrid ARQ Indicator Channel
PRACH Physical Random Access Channel
PRB Physical Resource Block
PUCCH Physical Uplink Control Channel
PUSCH Physical Uplink Shared Channel
QoS Quality of Service
QPSK Quadrature Phase Shift Keying
RAR Random Access Response
RRC Radio Resource Control
RX Receive
SC-FDMA Single Carrier Frequency Division Multiple Access
SCell Secondary Cell
SCH Shared Channel
SIB System Information Block
SINR Signal-to-Interference-Plus-Noise Ratio
SR Scheduling Request
TB Transport Block
TBS Transport Block Size
TDD Time-Division Duplex
TDM Time Division Multiplex
TX Transmit
UCI Uplink Control Information
UE User Entity/Equipment (Mobile Terminal)
UL Uplink
UMTS Universal Mobile Telecommunications System
WiMAX Worldwide Interoperability for Microwave Access
In wireless communications networks, DL TBs may be carried on the PDSCH. A maximum of two TBs may be transmitted on PDSCH in one serving cell and in a subframe. “HARQ-ACK” may represent collectively the Positive Acknowledge (“ACK”) and the Negative Acknowledge (“NAK”). ACK means that a TB is correctly received while NAK means a TB is erroneously received.
HARQ-ACK feedback bits corresponding to a PDSCH may be transmitted either on the PUCCH or on the PUSCH. For 3GPP Release 8 LTE FDD, HARQ-ACK feedback bits corresponding to PDSCH received in subframe n−4 are transmitted in subframe n. See 3GPP TS36.213 v12.6.0. Furthermore, for 3GPP Release 8 LTE TDD, HARQ-ACK feedback bits corresponding to PDSCH received in subframe n-k, where k belongs to the set K, are transmitted in subframe n. It should be noted that for LTE TDD, the elements in set K depends on the TDD UL/DL configuration, as well as the subframe index n, as shown in Table 1.
TABLE 1UL/DLSubframe nConfiguration01234567890——6—4——6—41——7, 64———7, 64—2——8, 7, 4, 6————8, 7, 4, 6——3——7, 6, 116, 55, 4—————4——12, 8, 7, 116, 5, 4, 7——————5——13, 12, 9, 8, 7, 5, 4, 11, 6———————6——775——77—
The LTE TDD UL/DL configurations are shown in Table 2. It should be noted that in Table 2, “D” represents a DL subframe, “U” represents an UL subframe, and “S” represents a special subframe. The timing relationship between the subframe containing the PDSCH and the subframe containing the corresponding HARQ-ACK feedback may be referred to as the HARQ timing.
TABLE 2Downlink-to-UplinkUplink-Switch-downlinkpointSubframe numberconfigurationperiodicity012345678905 msDSUUUDSUUU15 msDSUUDDSUUD25 msDSUDDDSUDD310 ms DSUUUDDDDD410 ms DSUUDDDDDD510 ms DSUDDDDDDD65 msDSUUUDSUUD
A frame structure for LTE FDD may be used in certain configurations. A radio frame of 10 milliseconds (“ms”) may include 10 subframes, each of which is 1 ms. Each subframe further may include two slots, each of which is 0.5 ms. Within each slot, a number of OFDM symbols may be transmitted. The transmitted signal in each slot on an antenna port may be described by a resource grid comprising NRBDLNscRB subcarriers and NsymbDL OFDM symbols, where NRBDL is number of RBs in the DL (which is dependent on the transmission bandwidth of a cell); NscRB is the number of subcarriers in each RB; and each subcarrier occupies a certain frequency of size Δf. The values of NscRB, Δf, and NsymbDL may depend on a cyclic prefix as shown in Table 3.
TABLE 3ConfigurationNscRBNsymbDLNormal Cyclic PrefixΔf = 15 kHz127Extended Cyclic PrefixΔf = 15 kHz6Δf = 7.5 kHz243
In certain configurations, an antenna port may refer to a logical antenna port (i.e., it may not necessarily refer to a physical antenna or antenna element). Mapping between an antenna port and physical antenna element(s) may be implementation specific. In other words, different devices may have a different mapping of physical antenna element(s) to the same antenna port. A receiving device may assume that the signals transmitted on the same antenna port go through the same channel. Moreover, a receiving device cannot assume signals transmitted on different antenna ports go through the same channel.
In certain configurations, carrier aggregation may be used such that more than one carrier may be aggregated by a UE to improve a transmission data rate. A UE may be able to aggregate a different number of carriers in the downlink and the uplink. For an RRC_CONNECTED UE (e.g., a UE in which an RRC connection has been established), each of the aggregated carriers may be a serving cell for the UE. Among the multiple aggregated serving cells, only one cell may be the primary cell while the other cells are secondary cells. In some configurations, PUCCH may be transmitted on both the primary cell and a secondary cell. Accordingly, PUCCH overhead may be offloaded from the primary cell to a secondary cell.
In some configurations, as part of carrier aggregation, aggregation of serving cells on a licensed spectrum and an unlicensed spectrum is supported for DL transmission. In such configurations, the serving cells in the unlicensed spectrum may only be secondary cells to a UE. The operation on the unlicensed carriers is assisted by the operation on the licensed carriers, hence the name licensed assisted access (“LAA”).
In certain configurations, LAA includes UL support for LAA secondary cell operation in an unlicensed spectrum. LAA may also allow for fair coexistence between Wi-Fi and LAA and fair coexistence between different LAA systems. Coexistence measures may still allow efficient operation of all coexisting technologies. PUCCH transmission may be performed on unlicensed carriers to offload PUCCH overhead from licensed carriers to unlicensed carriers. In order to support dual connectivity for LAA operation (e.g., the network node hosting the licensed carriers and the network node hosting the unlicensed carriers are geographically non-collocated and connected with non-ideal backhaul), PUCCH transmission in unlicensed carriers may be supported.
In various configurations, if there are a large number of carriers in the unlicensed spectrum and a limited number of carriers in licensed spectrum, it may be useful to offload some UCI from the licensed spectrum to the unlicensed spectrum. In some situations, the channel quality of the unlicensed spectrum may be worse than the channel quality of the licensed spectrum and there may be unpredictable channel access of unlicensed spectrum. Accordingly, HARQ-ACK corresponding to PDSCH in licensed spectrum may be transmitted in the licensed spectrum. Furthermore, HARQ-ACK transmitted in the uplink on an unlicensed spectrum may correspond to PDSCH transmitted on the unlicensed spectrum. This may be facilitated by eNB configuration.
As may be appreciated, LBT may be performed before transmissions on an unlicensed spectrum to facilitate fair coexist with other wireless systems on the same unlicensed spectrum. Moreover, for HARQ-ACK transmissions on an unlicensed carriers, LBT may be performed before actual HARQ-ACK transmissions. After an LBT is successful, a UE may start a HARQ-ACK transmission in the LAA uplink subframe according to a DL HARQ timing relationship. In contrast, HARQ-ACK transmission corresponding to DL transmission in an LAA secondary cell may not be transmitted on an LAA secondary cell uplink in response to a failed LBT for uplink channel access. Not transmitting a HARQ-ACK transmission may reduce DL throughput performance.